Functions
2.33 Interturn Protection (ANSI 59N (IT))
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
238
2.33.2 Setting Notes
General
The interturn fault protection is only in effect and accessible if address 155 INTERTURN PROT is set to during
configuration of protective functions.
Also it has to be specified in the Power System Data 1 that the input U
E
is used for the interturn fault protection.
The setting can be made at address 223 UE CONNECTION = Uen-winding. For factor U
E
(address 224) the
ratio of the phase-to-earth voltage to the voltage at the broken delta winding (U
E
input) is set according to
section 2.5.
The address 5501 INTERTURN PROT serves to switch the function ON or OFF or to block only the trip command
(Block relay).
Pickup Value
It is desired that the protection has a high sensitivity in order to already detect a fault when it has affected only
a few turns. On the other hand, an excessively sensitive setting should not cause overfunctioning. This is why
the default setting is 2 % which at a maximum secondary displacement voltage of 100 V corresponds to a
pickup value of 2 V.
The final pickup value has to be determined in primary tests. Pickup without an interturn fault being actually
present must be excluded! The protection function must not pick up erroneously on interference. Interference
is caused by winding asymmetries of the stator winding. Especially in case of a two-pole fault it becomes
obvious by the formation of a displacement voltage. Short-circuit tests should be conducted so as to determine
this interfering displacement voltage The protection range can thus be determined. The setting should be so
as to ensure that the function picks up on a interturn fault at no-load excitation. It should be able to detect a
fault already when it affects only one turn.
For the sensitive setting the dropout ratio may have to be reduced slightly. The default setting is 80 % (see
address 5504 RESET RATIO).
Delays
Delaying the protective function additionally reduces the risk of overfunctioning. But if the delay is too long,
there is a risk of the affected stator winding/core taking considerable damage. This is why the default value is
(see address 5503 T-U Interturn >).
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